Carbon films can exhibit a variety of desirable properties and therefore can be used for a variety of applications. For example, carbon films can be used for electrical energy storage, methane storage, hydrogen storage, as battery components (e.g., as anode material in a lithium-ion cell), as catalyst material or a catalyst support, for coatings, for microelectronic applications (e.g., logic devices, capacitors, or as hard masks), and for carbon nanotube and nanocrystal applications.
The carbon films are typically formed using chemical vapor deposition (CVD) or physical vapor deposition (PVD) techniques. Although such techniques can work relatively well for some applications, it can be relatively difficult to control the structure, morphology, and thickness of the deposited layers. Moreover, typical techniques for depositing carbon are not suitable for forming conformal films over high aspect ratio features.
Recently, techniques have been developed to form carbon films by depositing a metal carbide layer using CVD or PVD techniques and then exposing the metal carbide layer to chlorine or another reactant to remove the metal from the metal carbide film. Such techniques produce carbon films that generally follow the original shape or form of the initial metal carbide film. The CVD and PVD methods used to form the metal carbide films generally suffer from the same deficiencies of typical methods used to deposit carbon films, namely, the thickness of the deposited films is relatively difficult to control, and such techniques do not lend themselves to formation of conformal films, especially when formed overlying high-aspect ratio features. Accordingly, improved methods and systems to form conformal carbon layers and structures and devices including the layers are desired.